Purification of Aryltriazoles

ABSTRACT

Impure aryltriazoles such as benzotriazole and tolyltriazole that are contaminated with dark colored impurities can be purified by conversion to an aryltriazole acid salt by treatment with aqueous acid. The aryltriazole acid salt is water soluble whereas the dark colored impurities are not. The aryltriazole acid salt solution is separated from the dark colored impurities and the aryltriazole acid salt is isolated by precipitation. The free aryltriazole may be recovered by neutralization with base.

This applicaiton is a divisional of co-pending U.S. application Ser. No.13/932,829, filed on Jul. 1, 2013.

FIELD OF INVENTION

This invention relates to an improved process for preparing lightlycolored or colorless aryltriazoles. Aqueous solutions of the anions ofsaid aryltriazoles are, in addition, clear and free of fine particulatematter. The color improvement of this process occurs when impurearyltriazoles are solubilized in acidic solution and separated in theliquid phase from dark, insoluble impurities. The process of the presentinvention greatly reduces or eliminates the need for filtration, coloradsorption or distillation.

BACKGROUND OF THE INVENTION

The first reference to the preparation of aryltriazoles is Berichte 9,219 (1876) in which benzotriazoles and tolyltriazoles were prepared. Indescribing this process for purifying aryltriazoles, we specificallyinclude benzotriazole, tolyltriazole and alkyl-substituted analogs ofboth. The term tolyltriazole is meant to mean 4-methylbenzotriazole,5-methylbenzotriazole and mixtures of the two. Non-proprietary processesfor the preparation of aryltriazoles were subsequently published in Ber.Chem. 33, 261 (1900), Gazz. Chim. Ital. 51, 267 (1921), J. Chem. Soc.954 (1926), J. Am. Chem. Soc. 57, 1835 (1935), Organic Synthesis 20, 16(1940), and Chem. Berichte 100, 1646 (1967). Proprietary references tothe preparation of aryltriazoles are U.S. Pat. No. 2,861,078 (1958),U.S. Pat. No. 3,227,726 (1966), U.S. Pat. No. 3,637,514 (1972),DT2,351,595 (1973), U.S. Pat. No. 3,732,239 (1973), JP51-65760 (1976),U.S. Pat. No. 4,158,660 (1979), GB1,581,407 (1980), U.S. Pat. No.4,299,965(1981), U.S. Pat. No. 4,363,914 (1982), U.S. Pat. No. 4,424,360(1984), U.S. Pat. No. 4,528,381 (1985), U.S. Pat. No. 4,549,026 (1985),and U.S. Pat. No. 5,914,409 (1999).

Generally, these methods of preparation produce an aryltriazole productthat is darkened and discolored by various impurities. Some processeseven produce aryltriazole products that are black. The freearyltriazole, that is an aryltriazole that is not in its anionic form,is insoluble in aqueous solutions and is often isolated from aqueoussolutions as a solid or a melt. Such solids or melts usually containmost of the colorizing impurities initially in the aqueous solution.Such impurities are typically generated during the reaction processesthat convert o-aryldiamines to aryltriazoles. Such impurities may alsobe introduced into the product aryltriazoles as impurities in theo-aryldiamine starting materials. The dark and colored impurities havebeen described variously as “colored-bodies” or “tars”. The exact natureof the colored impurities has been long conjectured, and likely includemonoarylamines, monoaryldiazonium compounds, dimers ofmeta-aryldiamines, etc. The exact nature is of little consequence as thecolored impurity bulk likely consists of many or all these components.References to the purification of aryltriazoles are U.S. Pat. No.3,334,054 (1967), U.S. Pat. No. 3,564,001 (1971), U.S. Pat. No.3,639,431 (1972), U.S. Pat. No. 3,970,667 (1976), U.S. Pat. No.4,170,521 (1979), U.S. Pat. No. 4,269,987 (1981), JP 56-016478 (1981),U.S. Pat. No. 4,269, 987 (1981), EP0303772 (1988), U.S. Pat. No.4,918,195 (1990), JP04-360879 (1992), CN1,821,232 (2006), and JP224,014(2007).

Specific methods of purification that have been disclosed includevarious distillation methodologies. Of consequence is that the coloredimpurities exhibit very similar boiling points, making separation bydistillation difficult. Some components of the colored impurities boilat slightly lower temperatures than the target aryltriazoles while theremainder boil at higher temperatures, making fractionation necessary.Some components of the colored impurities may actually azeotrope withthe target aryltriazole, making complete separation by a singledistillation impossible. Also, colored impurities may entrain with thedistillate stream, carrying droplets of higher boiling colored impurityto the overheads and contaminating the final product. Generally, becauseof the high boiling point of the aryltriazoles, high-vacuum distillationis necessary to prevent decomposition of the aryltriazole and to keeptemperatures within safe ranges. In some cases, additives or specialconditions are used. U.S. Pat. No. 4,918,195 and EP0308772 teach thatdistillation from basic compounds, i.e. NaOH, reduces the color of thedistillate to a yellow which over time changes to grey. Similarly, U.S.Pat. No. 4,170,521 discloses the distillation of aryltriazoles fromformaldehyde to generate benzotriazole and tolyltriazole of reducedcolor. In some cases, the aryltriazole is co-distilled or azeotropedwith another compound to ease the distillation and improve yield. Forexample, U.S. Pat. No. 3,639,431 discloses the co-distillion ofbenzotriazole with polyethylene glycols. The distillate is anaryltriazole/polyethylene glycol mixture intended to be marketed as themixture. Distillation has the disadvantage of needing expensiveequipment. Another disadvantage is the concentration of high energyby-products in the still bottoms and the accompanying safety risks.

Another method of purification of aryltriazoles from colored impuritiesis adsorbance onto decolorizing media. Activated carbon, kieselguhr,diatomacious earth, clays, alumina, fuller's earth, pumice and sodiumdithionite may be used to remove colored impurities from solutions ofaryltriazoles. In many cases, the aryltriazole was in the anionic form,or was converted into the anionic form through the action of base,commonly hydroxide. For example, U.S. Pat. No. 3,970,667 discloses theuse of active carbon, kieselguhr and then sodium dithionite sequentiallyto purify a sodium tolyltriazole solution. Once the anionic form of thearyltriazole is sufficiently purified, it is generally recovered byacidifying the solution to a pH of about 5 or 6 wherein the freearyltriazole is regenerated and separates from solution as the solid ormelt, depending on temperature. U.S. Pat. No. 3,334,054 discloses adecolorization process in glycol solutions rather than aqueoussolutions. JP04-360879 discloses performing the decolorization firstunder basic (alkaline) conditions, then repeats under acidic conditionsbefore neutralizing and isolating the product. Unfortunately, thearyltriazole is also adsorbed onto the decolorizing media to someextent. As large quantities of decolorizing media are generally requiredto obtain acceptably purified aryltriazole, losses of aryltriazole toadsorption onto the media are appreciable. Also, large quantities ofadsorbant must be used and subsequently disposed. In U.S. Pat. No.3,970,667, 75 weight percent carbon plus 10 weight percent kieselguhrplus 10 weight percent sodium dithionite is used to effectdecolorization. All these decolorization processes have the distinctdisadvantage of handling solid decolorizing reagent, making addition andremoval cumbersome.

Another method of purification of aryltriazoles from colored impuritiesis crystallization. For example, benzotriazole and/or tolyltriazole havebeen crystallized from alcohols, benzene, cyclohexane, and xylenes.However, U.S. Pat. No. 3,637,514 and U.S. Pat. No. 3,732,239 (sameinventors) teach that there are colored contaminants in thearyltriazoles which cannot be removed by crystallization of the freearyltriazole. Crystallization is also inherently a low yield process.Though aryltriazoles are poorly soluble in cold and ambient temperaturewater, they have some solubility in hot water. Unfortunately, thecolored impurities share the same property. Attempts to recrystallizefree aryltriazoles from aqueous media typically precipitate the productwith the colored impurities included. Generally, the aryltriazoleseparates as a melt, rather than a solid, and again, includes thecolored impurities with it. The aryltriazole may be rendered soluble atambient temperature by conversion to the aryltriazole anion with aqueousbase. In this case, the colored impurities are also solubilized,generating a dark aqueous solution. Neutralization to a pH of about 5 or6 regenerates the free aryltriazole, which precipitates as a solid or anoil. Without fail, the colored impurities are included in theprecipitate, regenerating the discolored aryltriazole separated from anearly colorless aqueous solution.

In the prior literature, aryl triazoles have been manipulated as thefree aryltriazole under neutral conditions or as the aryltriazole anionunder basic (alkaline) conditions. It has now been found thatpurification of aryltriazoles can be readily achieved by converting thearyltriazole to its cationic form under acidic conditions and separatingthe soluble aryltriazolium acid salt from the insoluble dark impuritiesby simple liquid/liquid phase separation.

SUMMARY OF INVENTION

I have found that contrary to the above cases of mutual solubility,aryltriazoles and their accompanying colored bodies exhibit differingsolubilities in acidic aqueous media and that this property may beutilized to efficiently separate the two, thereby purifying thearyltriazole. In the preferred embodiment of this invention, thearyltriazole is fully solubilized by protonating the aryltriazole to itscationic salt with strong acid. Strong acids include the strong mineralacids, for example sulfuric acid, hydrochloric acid, nitric acid,phosphoric acid or perchloric acid. The colored impurities, whetherprotonated or not, remain insoluble in the acidic aqueous media and areremoved as a separate liquid phase. The colored impurities may beremoved in bulk without the disadvantages of using large quantities ofdecolorizing media, dangerous distillation techniques, or the handlingof solids.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In a preferred embodiment of this invention, as step 1, a sample ofaryltriazole, black with colored impurities, is dissolved in 1equivalent of hot 10 to 20% strong mineral acid to yield a biphasicliquid system. The (generally) upper layer consists of a solution of thearyltriazolium acid salt. The (generally) lower layer consists ofessentially the colored impurities as a heavy black oil. As step 2, thetwo phases are separated. The aryltriazole acid salt layer may be drawnoff or decanted. The color-body layer may also be drawn off convenientlyas a liquid phase and sent to disposal, recycle or other manipulation.As step 3, aryltriazole acid salt layer is neutralized with basesolution to release the free aryltriazole as a phase that is thenseparated from the aqueous components.

In step 1, it is preferable that at least 1 equivalent of strong mineralacid be used to solubilize the aryltriazole in its entirety. In the mostpreferred embodiment, the acid is sulfuric acid. As sulfuric acid is adiprotic acid, at least 0.5 moles of H₂SO₄ per 1.0 moles of aryltriazoleis preferable. The diprotic sulfuric acid apparently is able toprotonate and solubilize two individual aryltriazole molecules as thearyltriazole sulfate, though the solution may contain the aryltriazoliumsulfate and/or the aryltriazolium bisulfate. The use of less than 1equivalent of a strong acid generally leaves a portion of thearyltriazole unsolubilized with the loss of yield. In addition, itappears that under these conditions, the colored impurities continue tobe entrained into the aqueous layer to some extent and discolor theaqueous layer. It is allowable to utilize more than 1 equivalent ofstrong acid to solubilize the aryltriazole without detrimental effect.For example 1.0 mole of aqueous H₂SO₄ per 1.0 mole of aryltriazoleresults in a decolorized aryltriazole sulfuric acid salt solutionseparated from a black colored impurities oil layer. In effect, 2equivalents or stoicheometric H₂SO₄ have been used. The utilization ofmore than stoicheometric strong acid is not beneficial.

In step 2, the separation is preferably performed at elevatedtemperatures. I have found that while the aryltriazolium acid salts arereadily soluble in aqueous solution at temperature above about 50° C.and completely soluble above about 80° C. to 100° C., the colored-bodiesare not. In a closed vessel, temperatures may be above 100° C. withaccompanying pressures above 1 atmosphere. In addition, the coloredimpurity layer is maintained in a more fluid state at elevatedtemperatures, making drawing-off or decantation easier. In the preferredembodiment of this invention, separation is performed preferably above50° C., most preferably above 80° C.

According to step 3 of our invention, decolorized free aryl triazole maybe recovered from the decolorized aryltriazole acid solution byneutralization with aqueous base. Suitable bases are aqueous solutionsand slurries of NaOH, KOH, LiOH, Ca(OH)₂, Mg(OH)₂, NaHCO₃, Na₂CO₃,KHCO₃, K₂CO₃, LiHCO₃, Li₂CO₃, NH₄OH, etc. For example, titration withaqueous NaOH solution to a pH of 5 to 6 will precipitate decolorizedfree aryl triazole as a solid or a melt, depending on temperature. Ifdesired, the free aryl triazole may be further treated with base toconvert it to the anionic salt of the aryltriazole, i.e. sodiumbenzotriazole or sodium tolyltriazole. This may be performed as onestep, treating the aryltriazole acid salt solution with enough base toneutralize the aryltriazolium acid salt plus another equivalent todeprotonate the free aryltriazole, or the process may be performedsequentially by first neutralizing the aryltriazolium acid salt andseparating the free aryltriazole from the neutralized aqueous layer,then, in a second step, deprotonating the isolated free aryltriazolewith aqueous base. The latter has the advantage of generating solutionsof aryltriazole anion that are free of the salts of the parent strongacid and solutions that are more concentrated in aryltriazole anion.

It has been discovered further that in the process of our invention, theacidic aryltriazolium salt solution separated in step 2 may be purifiedfurther by precipitation of the solid aryltriazolium acid salt. Thearyltriazole acid salts are poorly soluble at less than about 20° C.(room temperature) and very poorly soluble at temperatures less thanabout 0° C. By cooling the aryltriazolium acid solution separated instep 2 to room temperature or below, even further purifiedaryltriazolium acid salts precipitate. As such, in the case of sulfuricacid, a hot yellow solution of tolytriazolium sulfuric acid salt uponcooling precipitates as snow white solid tolyltriazolium sulfuric acidsalt which is filtered from the residual aqueous solution. The coloredimpurities remain dissolved in the residual aqueous solution. As thefilter cake of the aryltriazolium salt tends to hold excess residualaqueous solution, it may be desired to recrystallize the aryltriazoliumsalt from hot water or hot aqueous acid, or simply rinse the cake withthe cold water or cold aqueous acid. The further purified aryltriazoleacid salt may then be submitted to step 3 of the process of the presentinvention for isolation of the free aryltriazole.

In a further embodiment of this invention, the residual aqueous solutionfrom aryltriazolium acid salt precipitation may be recycled to theoriginal acidification/separation step as it is a source of recyclablewater and acid (pH remains 0 to 1). Further, upon recycle, many of theresidual colored impurities are incorporated into the next coloredimpurities oil layer and, through saturation effects, are continuouslyremoved with each recycle. For those colored impurities not removed byrecycle, it has been found that passing the acidic residual aqueoussolution through a bed of adsorbent media, such as carbon, effectivelydecolorizes and reconditions the mother liquor whereupon it may berecycled or disposed.

If desired, the acidic aryltriazolium acid solution separated in step 2may be purified further by treatment with any of the applicable priorart methodologies. For example, the aryltriazolium acid salt solutionmay be passed through a bed of adsorbent media such as decolorizingcarbon. This material has been found to reduce the color of such asolution from Gardner ˜10 to Gardner 0.4. This is a vast improvement onthe prior art as it has been found that much less carbon is necessary toeffect the decolorization, the decolorization occurs at much faster flowrates, and the final color is much lighter than the directdecolorization methods. One adsorption media that we have discovered tobe effective that is not in the prior art is the “oil only adsorbentmedia”, commercially known a PIGs. In the form of sheets, pads or flock,“oil only adsorbents” are effective for removing residual coloredimpurity suspensions from the aryltriazolium acid solution. Conversely,we have found that “oil only adsorbents” are ineffective in decolorizingbasic (alkaline) solutions of aryltriazole anions.

If desired, after isolating the free aryltriazole resulting from step 3of this process, the aryltriazole may be subjected to furtherpurification by any of the applicable prior art methodologies. Forexample the free aryltriazole may be recrystallized from any of thesolvents listed above. The advantage here is that the feedstock for thecrystallization has been already purified by the process of ourinvention and as such produces crystals and precipitates of improvedpurity. In addition, yields are higher as precipitation can be forced toa greater extent without the inclusion of colored impurities. The freearyltriazole may also be further purified by any of the distillationmethods described in the prior art. The advantage here is that thefeedstock for distillation has already been purified by the process ofour invention and thus the entrainment of colored impurities is greatlyreduced. Yields are improved and hazards nearly eliminated as the amountof still bottoms (as high energy colored impurities) has been reduced tonegligible.

It has been discovered further that in the process of our invention,aryltriazolium acid salts may be used as a catalyst in the originalsynthetic reactions that generate aryltriazoles. There are alsoadvantages in doing so. It has been shown in the literature that weakacids may be used advantageously as catalysts for the preparation ofaryltriazoles from o-aryldiamines and nitrite salts. For example, aceticacid, citric acid, carbonic acid, glycolic acid, dihydrogen phosphate,oxalic acid, malonic acid, succinic acid, diglycolic acid, alkali metalbisulfates, alkanoic acids, benzoic acid and phthalic acid are disclosedas suitable weak acid catalysts. The free aryltriazole itself may beused as the acid catalyst and examples use about 6 mole percent. Adisadvantage in using the free aryltriazole is that it must beintroduced as a solid or freeze-prone melt. I have found that a portionof the aryltriazolium acid salt prepared by the process of our inventionmay be introduced to the original reaction of o-aryldiamines and nitritesalts as the weak acid catalyst with good effect. The biggest advantageis that the aryltriazolium acid salt may be conveniently introduced asan aqueous solution. Additionally the aryltriazolium sulfuric acid saltintroduces two equivalents of acid for each mole of aryltriazole. Thisresults in an approximately ⅓ reduction in the required mass ofcatalyst. As set forth in the specification herein, it is recognizedfrom the above examples that a catalytically effective amount of weakacid is about 1 mole percent to about 10 mole percent weak acid. Theweak acid is formally catalytic, that is it is neither consumed norproduced in the reaction. As such, the original nature of the reactionis not changed. For example, when the sodium salt of nitrous acid(sodium nitrite) is used as the nitration reagent, the sodium salt ofthe aryltriazole is produced. While it is typical to use the samearyltriazole acid salt as the aryltriazole to be produced by thereaction, there is nothing that precludes using a different aryltriazolesalt to catalyze the reaction so long as mixed aryltriazoles arecommercially acceptable in the final product. For examplebenzotriazolium sulfate may be used as catalyst for the reaction ofo-toluenediamine with sodium nitrite to form tolyltriazole.

In this invention, it has been shown that crude, highly coloredaryltriazoles may conveniently be purified by liquid/liquid separationof the colored impurities from the aryltriazoles. Central to the processof this invention is the treatment of the crude aryltriazole with anaqueous solution of a strong acid so as to completely solubilize thearyltriazole as its aryltriazolium acid salt. Strong acids include themineral acids, sulfuric, phosphoric, nitric, perchloric and hydrochloricacid. These strong acids are by no means equivalent as theiraryltriazolium acid salts vary in solubility and the acids themselvesvary greatly in cost. Sulfuric acid is the least expensive and has goodsolubility characteristics. None-the-less, each acid bears potentialusefulness within the scope of this invention.

Advantages of the present invention include the ability to purifyaryltriazoles without the handling of solid reagents. The liquid/liquidprocess described allows the convenient and continuous pumping of liquidphases. A further advantage of the present invention is that impuritiesare separated and isolated at moderate temperatures that avoid risk ofexplosion or exothermic reaction. Such waste streams are also notrendered anhydrous, thus increasing their stability.

EXAMPLES

The following examples are for the purpose of illustration only and arenot meant to limit the invention in any way.

Example 1 Isolation of Crude Tolyltriazole

500 g (1.58 mol) of crude 50% aqueous sodium tolyltriazole (black) wasplaced in a 2000 ml 3 necked flask. The solution was warmed to 60° C.with continuous stirring. The solution was titrated with 169.4 g (0.85mol) of a solution of 50% aqueous H₂SO₄ to a pH of 5.25 and atemperature of 84° C. The mixture was transferred to a preheatedseparatory funnel and held in an 80° C. oven until complete separationhad occurred. Upon draining, 261.5 g (1.55 mol) of a black oil wasisolated that was 79% free tolyltriazole and 16% water

Example 2 Liquid/Liquid Phase Separation of Dark Bodies fromTolyltriazole

13.3 g crude tolyltriazole oil (black) was stirred vigorously with 100 gof a hot solution of 10% H₂SO₄ in an erlenmeyer flask whereupon themajority of oil dissolved. The mixture was transferred to preheatedseparatory funnel and held in an 80° C. oven until complete separationhad occurred. A small amount of black oil was observed as the bottomphase and adhering to the separatory funnel. The remaining upper phasewas decanted off as a slightly yellow solution of the tolyltriazoliumacid salt. This yellow solution had a Gardner color of 10.8.

The above experiment was repeated with only 90 g of 10% H₂SO₄. In thiscase, separation was incomplete and the upper layer was dark and oily.

The above experiment was repeated with 110 g of 10% H₂SO₄. In this case,separation was again complete and the upper layer was slightly yellowwith a Gardner color of 10.8.

Example 3 Liquid/Liquid Phase Separation of Dark Bodies fromTolyltriazole

171.2 g crude tolyltriazole oil (black) was stirred vigorously with 980g of a hot solution of 10% H₂SO₄ in an erlenmeyer flask whereupon themajority of oil dissolved. The mixture was transferred to preheatedseparatory funnel and held in an 80° C. oven until complete separationhad occurred. Upon separation, 3.4 g of black oil was removed as thebottom phase while the remaining upper phase was a slightly yellowsolution of acidified tolyltriazole. This yellow solution was quicklypassed through a bed of 66 g decolorizing carbon to yield a finalsolution with a Gardner color of 0.5.

Example 4 Preparation and Precipitation of Tolyltriazole HydrogensulfateSolution

66.5 g (0.5 mol) of 99% tolyltriazole flake was stirred vigorously with490 g (0.5 mol) of a hot solution of 10% H₂SO₄ in an erlenmeyer flaskwhereupon the entirety dissolved to form a yellow solution. The mixturewas allowed to cool overnight whereupon precipitation had occurred. Theprecipitate was vacuum filtered to yield 146.4 g of a white filter cake.The cake proved to be 44% by weight of water, inferring a ‘dry’ yield of82 g. This corresponds to a 90% yield of (tolyltriazole)₂.H₂SO₄. The pHof the residual liquor was 0.2.

The above filter cake (0.225 mol) was suspended in 146 g H₂O andtitrated with 73.2 g (0.458 mol) of 25% NaOH to a pH of 5.45. Thiscorresponds to 101.6% of theoretical base for the neutralization of(tolyltriazole)₂.H₂SO₄.

Example 5 Preparation and Precipitation of Tolyltriazole SulfateSolution

133 g (1.0 mol) of 99% tolyltriazole flake was stirred vigorously with490 g (0.5 mol) of a hot solution of 10% H₂SO₄ in an erlenmeyer flaskwhereupon the entirety dissolved to form a yellow solution. The mixturewas allowed to cool overnight whereupon precipitation had occurred. Theprecipitate was vacuum filtered to yield 262.2 g of a white filter cake.The cake proved to be 44% by weight of water, inferring a ‘dry’ yield of147 g. This corresponds to an 80% yield of (tolyltriazole)₂.H₂SO₄. ThepH of the residual liquor was 0.1.

22 g of the above wet filter cake (0.039 mol) was suspended in 11 g H₂Oand titrated with 16 ml (0.032 mol) of 2M Na₂CO₃ to a pH of 5.27 at 55°C. This corresponds to 94% of theoretical base for the neutralization of(tolyltriazole)₂.H₂SO₄. The weight of isolated tolyltriazole was 8.47 g(0.064 mol) as a white solid. This corresponds to a 94% yield.

Example 6 Preparation and Precipitation of Benzotriazole HydrogensulfateSolution

59.6 g (0.50 mol) of 98% benzotriazole flake was stirred vigorously with245 g (0.50 mol) of a hot solution of 20% H₂SO₄ in an erlenmeyer flaskwhereupon the entirety dissolved to form a yellow solution. The mixturewas allowed to cool several hours in an ice-water bath whereuponprecipitation had occurred. The precipitate was vacuum filtered to yielda white filter cake. A second crop of precipitate was collected afterfurther cooling of the mother liquor. The combine weight of solidproduct was 97.2 g. The filter cake proved to be 11.6% by weight ofwater, inferring a ‘dry’ yield of 85.8 g. This corresponds to a 102%yield of (benzotriazole)₂.H₂SO₄. The pH of the residual liquor was 0.2.

Example 7 Preparation and Precipitation of Benzotriazole SulfateSolution

36.0 g (0.30 mol) of 98% benzotriazole flake was stirred vigorously with73.5 g (0.15 mol) of a hot solution of 20% H₂SO₄ in an erlenmeyer flaskwhereupon the entirety dissolved to form a yellow solution. The mixturewas allowed to cool several hours in an ice-water bath whereuponprecipitation had occurred. The precipitate was vacuum filtered to yielda white filter cake. A second crop of precipitate was collected afterfurther cooling of the mother liquor. The combine weight of solidproduct was 56.5 g. The filter cake proved to be 11.6% by weight ofwater, inferring a ‘dry’ yield of 50.0 g. This corresponds to a 98%yield of (benzotriazole)₂.H₂SO₄. The pH of the residual liquor was 0.1.

Example 8 Use of Benzotriazolium Sulfate as Catalyst for the Preparationof Benzotriazole from O-Diaminobenzene

108.0 g (1.0 mol) of o-diaminobenzene, 75.9 g (1.1 mol) NaNO₂, 205 gwater and 10.0 g (0.03 mol) benzotriazolium sulfate were charged to apressure reactor. The reaction was heated to 205° C. for 4 hours. Thereactor was cooled to 50° C. and neutralized to pH 6 with 50% H₂SO₄. Thecontents were poured into a preheated separatory funnel and separated.The resulting oil was dried overnight at 150° C. to yield 117 g (98%) ofbenzotriazole.

I claim:
 1. (canceled)
 2. The process according to claim 29 wherein theimpure aryltriazole is benzotriazole.
 3. The process according to claim29 wherein the impure aryltriazole is tolyltriazole.
 4. The processaccording to claim 29 wherein the strong acid is selected from the groupconsisting of sulfuric acid, hydrochloric acid, nitric acid, phosphoricacid and perchloric acid.
 5. The process according to claim 29 whereinthe strong acid is sulfuric acid.
 6. The process according to claim 29wherein the strong acid is selected from the group consisting ofphosphoric acid and nitric acid.
 7. (canceled)
 8. (canceled) 9.(canceled)
 10. (canceled)
 11. (canceled)
 12. The process according toclaim 29 wherein said dissolving is carried out using at least 1equivalent of strong acid per mole of aryltriazole.
 13. The processaccording to claim 29 wherein said dissolving is carried out using atleast 0.5 moles (1 equivalent) of sulfuric acid per mole ofaryltriazole.
 14. The process according to claim 29 wherein saiddissolving is carried out using at least 1.0 moles (1 equivalent) ofstrong acid selected from the group consisting of hydrochloric andnitric acid per mole of aryltriazole.
 15. The process according to claim29, step 2 wherein said reacting is carried out at a temperature of fromabout 50 degrees centigrade to about 100 degrees centigrade (Celsius).16. The process according to claim 29, step 2 wherein said temperatureis carried out at a temperature of from about 80 degrees centigrade toabout 100 degrees centigrade (Celsius).
 17. The process according toclaim 29, whereas said solid cationic form of said aryltriazole istreated with an aqueous solution of base to form an aqueous solutioncontaining the anionic form of said aryltriazole.
 18. The processaccording to claim 29 wherein said salt solution of step 4 is recycledto form a recycle liquid, forming a solution of an impure aryltriazolewith a 10-20% aqueous solution of a strong acid using said recycleliquid as the solvent, to form two liquid phases, one phase of said twoliquid phases comprising the cationic form of said aryltriazole and theother phase of said two liquid phases comprising substantially all ofthe dark and colored impurities, and repeating steps 2, 3 and
 4. 19.(canceled)
 20. (canceled)
 21. (canceled)
 22. In a process for thepreparation of purified aryltriazoles by the reaction of o-aryldiamineswith nitrite salts, the improvement comprising acidifying the reactionproduct of said reaction of o-aryldiamines with a nitrite salt therebyforming an aqueous solution of a purified aryltriazole in an aqueoussolvent, and separating a purified solid aryltriazole from a residualaqueous solvent solution.
 23. A process according to claim 29 whereinsaid residual aqueous solvent solution from an aryltriazolium acid saltsolution of Step 3 is purified by treating the solution with anadsorbing media selected from the group consisting of activated carbon,kieselguhr, diatomaceous earth, clays, alumina, fuller's earth, pumice,sodium dithionite, and “oil only” absorbents thereby forming a purifiedresidual aqueous phase.
 24. The process according to claim 29 whereinthe aqueous solution of the cationic form of said aryltriazole of Step 2is treated with an adsorbing media selected from the group consisting ofactivated carbon, kieselguhr, diatomaceous earth, clays, alumina,fuller's earth, pumice, sodium dithionite and “oil only” absorbentsthereby forming a further purified aqueous aryltriazole salt solution.28. The process according to claim 29 wherein the aqueous solution ofthe cationic form of said aryltriazole acid salt solution of Step 2 istreated with an adsorbing media consisting of “oil only” absorbents. 29.A process for purifying an impure aryltriazole obtained by thediazotization reaction of an ortho-phenylenediamine with a nitrite, saidimpure aryltriazole containing dark and colored impurities, consistingof the steps: 1) dissolving at a temperature of 50 to 100° C. saidimpure aryltriazole with an aqueous solution of at least 1 equivalent ofa 10-20% aqueous solution of strong acid to form two liquid phases, onephase of said two liquid phases comprising the cationic form of saidaryltriazole in an aqueous solution and other phase of said two liquidphases comprising substantially all of the dark and colored impurities;2) separating the one phase of the said two liquid phases comprisingsaid cationic form of said aryltriazole in an aqueous solution from theother phase of the liquid mixture comprising substantially all of thedark and colored impurities; 3) cooling said one phase of the said twoliquid phases comprising said cationic form of said aryltriazole in anaqueous solution to less than 50° C., thereby forming two new phases,one phase being the solid cationic form of said aryltriazole and theother phase being an aqueous solution. 4) separating said solid cationicform of said aryltriazole from said aqueous solution.
 30. A process forpurifying impure tolyltriazole obtained by the diazotization reaction ofan ortho-toluenediamine with a nitrite, said impure tolyltriazolecontaining dark and colored impurities, consisting of the steps: 1)dissolving at a temperature of 80 to 100° C. said impure tolyltriazolewith an aqueous solution of at least 1 equivalent of a 10-20% aqueoussolution of sulfuric acid to form two liquid phases, one phase of saidtwo liquid phases comprising the cationic form of tolyltriazole in anaqueous solution and the other phase of said two liquid phasescomprising substantially all of the dark and colored impurities; 2)separating the one phase of the said two liquid phases comprising saidcationic form of tolyltriazole in an aqueous solution from the otherphase of the liquid mixture comprising substantially all of the dark andcolored impurities; 3) cooling said one phase of the said two liquidphases comprising said cationic form of tolyltriazole in an aqueoussolution to less than 50° C., thereby forming two new phases, one phasebeing the solid cationic form of said tolyltriazole and the other phasebeing an aqueous solution. 4) separating said solid cationic form ofsaid tolyltriazole from said aqueous solution.